rockpi4.c: fixed pwm issue

e.g.:
    cv2 import at the beginning throws the error:
    import cv2
    import mraa
    import time
    ...

    Error:
    ValueError: Error initialising PWM on pin

Signed-off-by: Brian Lee <brian@vamrs.com>

src/arm/rockpi4.c

@@ -115,7 +115,11 @@ mraa_rockpi4()
     }
 
     b->pins[11].pwm.parent_id = 0;
+    b->pins[11].pwm.mux_total = 0;
+    b->pins[11].pwm.pinmap = 0;
     b->pins[13].pwm.parent_id = 1;
+    b->pins[13].pwm.mux_total = 0;
+    b->pins[13].pwm.pinmap = 0;
 
     b->aio_count = MRAA_ROCKPI4_AIO_COUNT;
     b->adc_raw = 10;